Well, I need to say, it is really a myth. Our eyes‘ movements and the shape of the lens are controlled by some specialized muscles. I mean, your tiny muscles , which automatically control the lens, change its shape when one thing is close to you, bringing the object into the proper focus. We also all this process as accommodation. Further, those muscles keep the eyes moving in a synchronized way contracting and relaxing normally. Tiny muscles are resilient, although they will fatigue when you try to cross your eyes. The reason why people insist on the myth about eye crossing may be they do not want their children to do such annoying behavior.
